A cloak was an item of clothing, often worn on top of other clothes.
In the Sense Sphere, the First Doctor was given a cloak by the First Elder after his jacket was damaged. (TV: The Sensorites) The First Doctor also wore cloaks on other occasions, such as when he visited England in 1066 (TV: The Time Meddler) and Antarctica in December 1986. (TV: The Tenth Planet)
On Skaro, Alydon gave Susan Foreman a cloak, which was later used by the First Doctor and Ian Chesterton to disable a Dalek. (TV: The Daleks)